You are going to want to store and work with ethylene diamine in a hood because it is a fuming hygroscopic liquid. You will likely not find it except through a large (local) research chemical supply house. The free-base is nasty to handle but only a small quantity is needed. Once in the color developer solution it presents no further handling problem. You might have better luck locating the sulfate which is solid powder although it hydrolizes to a highly alkaline solution. However, since you use only a few grams it's probably not worse to handle than KOH.
